The signs, reading "Go home or face arrest," also list a text number people who have overstayed their visas can contact to arrange a trip back home without being arrested, The Guardian reported Monday.
The campaign targets six boroughs in London with either significantly higher or below average numbers of voluntary returns. It's supplemented by leaflets, posters and ads in newspapers.
Immigration Minister Mark Harper said while efforts by the government had made it harder for illegal immigrants to live and work in England, the campaign was "an alternative to being led away in handcuffs."
The program is part of a package of immigration reforms introduced this year.
Last year, more than 28,000 illegal immigrants went home voluntarily.